when using command parameter to pass dialog content, inherit data context from the button #124

Author: ButchersBoy

MainDemo.Wpf/Dialogs.xaml

@@ -105,7 +105,7 @@
                             wpf:DialogHost.DialogClosingAttached="Sample2_DialogHost_OnDialogClosing"
                             Width="128">
                         <Button.CommandParameter>
-                            <StackPanel Margin="16">
+                            <StackPanel Margin="16" DataContext="HelloWorld">
                                 <ProgressBar Style="{DynamicResource MaterialDesignCircularProgressBar}" HorizontalAlignment="Center" Margin="16" IsIndeterminate="True" Value="0" />
                                 <Button Style="{StaticResource MaterialDesignFlatButton}" IsCancel="True" 
                                         Command="{x:Static wpf:DialogHost.CloseDialogCommand}"

MaterialDesignThemes.Wpf/DialogHost.cs

@@ -437,7 +437,20 @@ private void OpenDialogHandler(object sender, ExecutedRoutedEventArgs executedRo
             if (executedRoutedEventArgs.Parameter != null)
             {
                 AssertTargetableContent();
-                DialogContent = executedRoutedEventArgs.Parameter;
+
+                //TODO enhancement: make the following configurable, so that the data context can be pulled from the dialog host if desired.
+                //      (leave the current behaviour as the default; most developers will find this logical, as the data context will "inherit" from button containing the content)
+
+                var contentElement = executedRoutedEventArgs.Parameter as FrameworkElement;
+                var senderElement = executedRoutedEventArgs.OriginalSource as FrameworkElement;
+                if (contentElement != null && senderElement != null && contentElement.DataContext == null && BindingOperations.GetBindingExpression(contentElement, DataContextProperty) == null)
+                {
+                    DialogContent = executedRoutedEventArgs.Parameter;
+                    contentElement.SetCurrentValue(DataContextProperty, senderElement.DataContext);
+                }
+                else
+                    DialogContent = executedRoutedEventArgs.Parameter;
+
             }
 
             SetCurrentValue(IsOpenProperty, true);